Prior art is replete with teachings of elongate support members and trusses that support applied loads along a span. Many planar or open-section beams have the capability of maintaining their in-plane structural integrity while having appreciable torsional flexibility however, they are limited in their ability to resist their out-of-plane loads comparable to closed section beams of similar dimensions. Controlled torsional resistance, while not claimed, was embodied in an open section beam whose resistance to torsional load would not approach that of a closed section beam with similar dimensions. Other non-planar beams resist more general loading but do not allow appreciable torsional flexibility. Further plenarily controlled torsional resistance beams were generally lacking in the prior art discovered.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however, the following U.S. patents were considered related:
______________________________________ PATENT NUMBER INVENTOR ISSUED ______________________________________ 4,221,400 Powers 21 June 1978 4,183,596 Greene, et al 17 January 1979 3,778,946 Wood, et al 18 September 1973 3,362,117 Van Raden 24 May 1963 3,279,141 Schmidt 18 October 1966 3,108,665 Marchant 29 October 1963 2,258,046 Clement 7 October 1941 2,089,023 Hahn 2 August 1937 1,949,818 Tarbox 6 March 1934 1,453,114 Rapp, et al 24 April 1923 ______________________________________
Powers teaches the means for adjusting the stiffness of a flexible body by the use of a prestressed curved rod member penetrating a bore with the stiffness adjusted by relocating the rod member at different positions about the longitudinal axis.
Wood et al discloses a planar truss with the camber automatically attained in the chords of the truss by means of tensioned tensors and compression members between the top and bottom chords of the truss.
Marchant utilizes a trellis work non planar structure for supporting rigid or articulated sections composed of metallic shaped sections having a flat bottom with cross stays drawn out into an attachable central portion.
Tarbox teaches a non planar truss member for aircraft with flat sheet metal parts with a portion readily joined to a longitudinal member. The truss is a combination of triangles formed with constituent cap strips and triangulated beading. Its embodiment would have only incidental torsional flexibility.
For background purposes and as indicative of the art to which the invention relates reference may be made to the remaining cited patents.